0w40 to replace 5w20?

[Johnny248]

After reading around, I *think* I know what everyone will say.

I have 12 gallons of M1 FS 0w40 that I acquired. Ive read the positive opinions and about it's cleaning ability. I'm currently running it in my '11 Ram 5.7l. The Dodge forums seem to have a lot of people running 0w/5w40 in their 5.7l Hemi engines with the reasoning behind it is that that 6.2l/6.4l spec it. Engine seems to run fine, possibly a little quieter. I do from time to time get a code for incorrect oil viscosity, but it does not throw a CEL or disable MDS.

I was considering using it in my 3.7l Liberty which although has low mileage, I know for a fact that it didn't necessarily have the best care before I picked it up. That engine calls for 5w20. I've been running 5w30 in it. Any reason not to use the M1 0w40 other than a possible decrease in fuel economy?

 

[JavierH19]

Many on here with 5.7's say the same, no codes or issues. Use it. Any mpg decrease would be very very miniscule. Probably 0.3mpg at most. Many will incorrectly test mpg and come to a wrong conclusion that it decreased it by a notable amount like 2 mpg which it didn't.

 

[Johnny248]

Many on here with 5.7's say the same, no codes or issues. Use it. Any mpg decrease would be very very miniscule. Probably 0.3mpg at most. Many will incorrectly test mpg and come to a wrong conclusion that it decreased it by a notable amount like 2 mpg which it didn't

My 5.7l just turned 170k. What is weird about the code is that sometimes it pops up, sometimes it doesn't. Like I said, I doesn't throw a CEL light, but if you scan codes it shows up. Not too worried about it. This truck's mpg varies so much depending on what it is doing, it's nearly impossible to ever know what the actual average is. I can go from 11 to 19 on the same tank, so not worried about that. I'm just wondering if there is any reason not to use it in the 3.7l.

 

[twX]

My 5.7l just turned 170k. What is weird about the code is that sometimes it pops up, sometimes it doesn't. Like I said, I doesn't throw a CEL light, but if you scan codes it shows up.

The code would be based on measured oil pressure at a given oil temperature. The code will be more likely to activate as your oil filter gets clogged up since oil pressure will go up. If you use an oversized oil filter with less restriction to flow, it might be enough to prevent the code entirely.

 

[Johnny248]

The code would be based on measured oil pressure at a given oil temperature. The code will be more likely to activate as your oil filter gets clogged up since oil pressure will go up. If you use an oversized oil filter with less restriction to flow, it might be enough to prevent the code entirely.

I didn't know there was an oversized filter available that fits? It's an xx2 in Fram numbers, and a Mobil M1-210A ( currently using because we stock them). I believe that these also fit Ford 5.4l among under things.

 

[tasch72]

I didn't know there was an oversized filter available that fits? It's an xx2 in Fram numbers, and a Mobil M1-210A ( currently using because we stock them). I believe that these also fit Ford 5.4l among under things.

There isn't an oversized filter for that application.

 

[JavierH19]

My 5.7l just turned 170k. What is weird about the code is that sometimes it pops up, sometimes it doesn't. Like I said, I doesn't throw a CEL light, but if you scan codes it shows up. Not too worried about it. This truck's mpg varies so much depending on what it is doing, it's nearly impossible to ever know what the actual average is. I can go from 11 to 19 on the same tank, so not worried about that. I'm just wondering if there is any reason not to use it in the 3.7l.

The 3.7 doesn't care what's it in and i don't think I've ever heard of it having problems with a different oil grade.

 

[wlk]

My Dakota had a 3.7 and it was spec'd 5w30, 0w40 will be fine in it

 

[addyguy]

I think the 0W-40 would be a great oil for the 3.7 to prevent timing-chain wear.

 

[Skippy722]

You’ll be fine. Ran 0w40 in my 3.6 pentastars at one point and they didn’t care. Probably going to switch my truck over to 0w40 once the warranty is up.

 

[Chris142]

Wait. They know what viscosity you are using now?

 

[Skippy722]

Wait. They know what viscosity you are using now?

Just Mopar weirdness, P1521. As twX said, it’s just inferring it based off oil pressure and temperature. I guess they REALLY want people using 0/5w20 for whatever reason even though the MDS system is identical to that found in the SRT and truck 6.4’s which call for 0w40.

 

[Triple_Se7en]

Wifey's Kia Soul specs 5w20 in the Owners Manual. But it seems to handle the SP-cert Pennzoil Euro 0w40 even better. No cold start engine chatter all thru last winter either.

 

[hand-filer]

Running 5W-40 PP Euro in my supercharged 5.0 for the last 2 oil changes. 10W-30 Amsoil Signature prior to that since new. It gets along well with the 5W-40. The factory specified 5W-20 was never a consideration.

 

[Sonny88]

Running a different grade other than 5W-20 threw a code on my 2021 3.6.
I had put 5W-30 in, (Mobil1) because I had it available.
Took about 15 miles, then engine light came on.
Drained it , and figured lesson learned.
After putting in proper oil, about 30 miles later, light went back off.

 

[SR5]

I would run the 0W40

 

[Snagglefoot]

The code would be based on measured oil pressure at a given oil temperature. The code will be more likely to activate as your oil filter gets clogged up since oil pressure will go up. If you use an oversized oil filter with less restriction to flow, it might be enough to prevent the code entirely.

Where exactly is the oil pressure being read on the engine? On a Chevrolet LS engine the oil pressure is being read downstream of the oil filter, so a clogged filter would actually lower the indicated pressure. In real life, the bypass in the filter opens.

 

[demarpaint]

Running a different grade other than 5W-20 threw a code on my 2021 3.6.
I had put 5W-30 in, (Mobil1) because I had it available.
Took about 15 miles, then engine light came on.
Drained it , and figured lesson learned.
After putting in proper oil, about 30 miles later, light went back off.

No problems at all running ESP 0w30 or 5w30 in my 2016 3.6L Wrangler. I've been running it for years now.

 

[ka9mnx]

As far as fuel mileage goes...I used 5w-20 in my 3.0 Ranger when it was new. This engine was originally spec'd for 5w-30. After a while I changed to 5w-30 (I'm a thicky). Engine seemed to run better (placebo?). Last year I moved up to 5w-40 Euro and the engine runs even better and quieter (more placebo?).

Now for the fuel economy. Never really had great fuel economy on 5w-20. There was a significant increase with 5w-30 (oil quality?). The verdict is out on the 5w-40 as my run was over the Winter (yea, South Carolina Winter) but seems a hair less than 5w-30. We'll see how the Summer goes with 5w-40.

Oil used:
5w-20 - Motorcraft
5w-30 - Some M1 but mostly SuperTech
5w-40 - Quaker State

 

[Triple_Se7en]

If that were my HEMI, I'd make a smaller move initially - to 0w30. If that fares real well in both sound and performance, then move to 0w40 next summer.